Widespread Divergence of the CEACAM/PSG Genes in Vertebrates and Humans Suggests Sensitivity to Selection

Chang, Chia Lin; Semyonov, Jenia; Cheng, Po Jen; Huang, Shang Yu; Park, Jae Il; Tsai, Huai-Jen; Lin, Cheng-Yung; Grützner, Frank; Soong, Yung Kuei; Cai, James J.; Hsu, Sheau Yu Teddy

It has been hypothesized that the repeated expansion of CEACAM/PSG genes in primates and rodents could be associated with positive selection of select members [22, 23] . The hypothesis is supported by the finding that PSG genes in apes and Rhesus monkeys could be derived from independent expansion even though Rhesus monkey ancestors diverged from those of humans only 25 million years ago. This observation led us to further hypothesize that the selection shaping CEACAM/PSG gene repertoire in apes could be ongoing, and human CEACAM/ PSG genes, as a group, could continue to diverge at a pace greater than that of other genes. To test this hypothesis, we investigated the extent of genetic variations (i.e., CNVs and SNPs) in human CEACAM/PSG genes, and whether the occurrence of CNVs and SNPs differs among human populations. In these analyses, richness and diversity of structural and nucleotide variations were used as proxies to determine the tendency for selection.